Controlled release NPK fertiliser encapsulated by a biodegradable polyester

The commercial NPK granular fertilizer was coated using a biodegradable polyester namely polylactic acid (PLA) in order to prepare controlled release NPK fertilizers (PLA coated NPK fertilizers). The coatings were prepared from the polymer solution of PLA by immersion method. The effects of PLA concentration (5, 15 and 25% w/v) and number of coating (single and double coatings) on nutrients release behaviour in water (in terms of conductivity) of PLA-coated NPK fertilizers were investigated at room temperature for a period of 28 days. The physical properties of the coatings affect the nutrient release rate. The results also revealed that the release of NPK nutrients from double PLA-coated NPK fertilizers were slower than that of single PLA-coated NPK fertilizers. The release of nutrients through the coating made up of 25% w/v of PLA was the slowest. Among the single and double PLA-coated fertilizers, only 25% w/v double PLA coated fertilizer (D25) meets the controlled release criteria by the European Committee for Standardization (CEN). Therefore, this study demonstrated that D25 could acts as controlled release fertilizers (CRFs) which are suitable for sustainable agricultural and horticultural applications.